SCS-C02 Infrastructure Security Practice Question

A company has an S3 bucket that contains sensitive data. The security team wants to ensure that all access to the bucket is encrypted in transit. Which policy should be attached to the bucket to enforce this?

⚠ Common exam trap

Many exam-takers confuse encryption in transit (HTTPS/TLS) with encryption at rest (SSE headers or default encryption), leading candidates to pick options that enforce server-side encryption instead of transport-layer security.

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

Attach a bucket policy that denies requests when aws:SecureTransport is false.

The `aws:SecureTransport` condition key in an S3 bucket policy evaluates whether the request was sent over HTTPS (TLS). By attaching a bucket policy that denies access when `aws:SecureTransport` is false, the security team enforces that all access to the bucket must be encrypted in transit, blocking any HTTP requests.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✗
Configure a bucket policy that denies requests that do not include the x-amz-server-side-encryption header.
Why it's wrong here
Denying requests without the x-amz-server-side-encryption header forces clients to declare a server-side encryption mechanism, but this only protects the object at rest in S3. The header has no effect on how the request traverses the network—data can still be sent over plain HTTP while the header is present. Thus, it does not enforce encryption in transit.
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Attach a bucket policy that denies requests when aws:SecureTransport is false.
Why this is correct
The aws:SecureTransport condition key is a boolean that is true only when the request is made over SSL/TLS. By attaching a bucket policy with a Deny effect when aws:SecureTransport is false, the bucket rejects every HTTP request and only allows HTTPS requests. This enforces encryption in transit for all S3 operations, including direct API calls from any client or SDK, making it the correct solution.
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Enable default encryption on the bucket using SSE-S3.
Why it's wrong here
Enabling default encryption with SSE-S3 ensures that S3 encrypts objects at the time of storage, but it does nothing to protect data during transmission. A client can still upload or download objects over HTTP, exposing the data in transit. This option is about at-rest encryption, not the transit requirement in the question.
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Use Amazon CloudFront to serve the content and require HTTPS.
Why it's wrong here
CloudFront can require HTTPS for end users, and you can configure the origin to use HTTPS as well, but this only protects traffic that goes through CloudFront's distribution. Users or applications that access the S3 bucket directly via the S3 API endpoint, bypassing CloudFront, can still use HTTP unless a bucket policy explicitly blocks insecure transport. Therefore, this is an incomplete solution for the stated requirement.

Quick reference

AWS S3 Storage Class Comparison

Storage Class	Min Duration	Retrieval	Use Case
S3 Standard	None	Immediate	Frequently accessed data
S3 Standard-IA	30 days	Immediate	Infrequent access, rapid retrieval
S3 One Zone-IA	30 days	Immediate	Non-critical infrequent data
S3 Intelligent-Tiering	None	Immediate–hours	Unknown or changing access patterns
S3 Glacier Instant	90 days	Milliseconds	Archive with instant retrieval
S3 Glacier Flexible	90 days	Minutes–hours	Archive, flexible retrieval
S3 Glacier Deep Archive	180 days	Hours	Long-term compliance archive

Go deeper

SCS-C02 Infrastructure Security Practice Question

Why each option matters

Option-by-option breakdown

AWS S3 Storage Class Comparison

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